Access Control Device, Access Control Method, Program, Storage Medium, and Integrated Circuit

1. An access control device for controlling accesses by users to image contents each including still image data or video image data, the access control device comprising: a storage circuit storing first user information in association with each of one or more persons, each piece of the first user information being a set of identification information of one or more users who are permitted by a person to access image contents including image data in which the person is a subject; an obtaining circuit obtaining an image content together with a piece of second user information, both having been transmitted from an external transmitter, the image content including image data in which one or more persons are subjects, and the piece of the second user information being a set of identification information of one or more users who are desired by the transmitter to be permitted to access the image content; and a control circuit (i) extracting, from the first user information, one or more pieces of identification information of one or more users who are permitted by all of the one or more persons, who are the subjects of the image data included in the image content obtained by the obtaining circuit, to access the image content and (ii) permitting a user to access the image content when the user is included among the one or more users indicated by the piece of the second user information and is included among the one or more users indicated by the one or more pieces of identification information extracted by the control circuit.

2. The access control device of claim 1 , wherein the persons are users of the access control device, and if there is an out-of-range user who is included in the users indicated by the piece of the second user information, but is not included in the users indicated by one or more pieces of the first user information, the control circuit requests each of users, who have set the one or more pieces of the first user information, to return a response indicating whether or not to permit the out-of-range user to access, and upon receiving a response indicating to permit the out-of-range user to access, gives permission to each user indicated by the piece of the second user information to access the image content obtained by the obtaining circuit.

3. The access control device of claim 2 , wherein, if the control circuit receives the response indicating to permit the out-of-range user to access, from the users who have set the one or more pieces of the first user information, the control circuit updates a piece of the first user information to include the out-of-range user in the users indicated by the piece of the first user information.

4. The access control device of claim 2 , wherein, if the control circuit receives the response indicating not to permit the out-of-range user to access, from the users who have set the one or more pieces of the first user information, the control circuit gives permission to the users indicated by the piece of second user information, except for the out-of-range user, to access the image content obtained by the obtaining circuit.

5. The access control device of claim 1 , wherein the persons are users of the access control device, and if the control circuit receives, from a user, an update request to update a piece of the first user information stored in the storage circuit in association with the user, the control circuit updates the piece of the first user information.

6. The access control device of claim 5 , wherein the control circuit further manages a piece of permitted user information and a piece of the second user information in association with each other for each image content obtained by the obtaining circuit, the piece of the permitted user information indicating users who are permitted to access the image content, the piece of the second user information being related to the image content, and when updating the piece of the first user information, the control circuit updates a piece of the permitted user information related to an image content including image data in which the user who transmitted the update request is a subject, based on (i) information indicating the piece of the first user information after the update and (ii) a piece of the second user information related to the image content.

7. The access control device of claim 1 , wherein the persons are users of the access control device, the control circuit further manages a piece of permitted user information and a piece of the second user information in association with each other for each image content obtained by the obtaining circuit, the piece of the permitted user information indicating users who are permitted to access the image content, the piece of the second user information being related to the image content, and if the control circuit receives, from a user, information indicating users whom the user has given permission to access an image content including image data in which the user is a subject, the control circuit updates a piece of the permitted user information related to the image content based on (i) the received information and (ii) a piece of the second user information related to the image content.

8. The access control device of claim 1 , wherein if the image content obtained by the obtaining circuit includes a plurality of pieces of image data in which, on a one-to-one correspondence basis, a plurality of users are subjects, the control circuit judges, for each of the plurality of pieces of image data, whether or not there is an out-of-range user who is not included in one or more users indicated by the first user information stored in the storage circuit in association with a user who is a subject in the piece of image data, but is included in one or more users indicated by the piece of the second user information, and if the control circuit judges that there is the out-of-range user, the control circuit requests the user, who is the subject in the piece of image data, to return a response indicating whether or not to permit the out-of-range user to access, upon receiving, from all of the users requested to return the response, the response indicating to permit the out-of-range user to access, the control circuit gives permission to the users indicated by the piece of the second user information to access the image content obtained by the obtaining circuit, and upon receiving, from any of the users requested to return the response, the response indicating not to permit the out-of-range user to access, the control circuit gives permission to the users indicated by the piece of the second user information, except for the out-of-range user, to access the image content obtained by the obtaining circuit.

9. The access control device of claim 8 , wherein, when the control circuit requests one or more users, who are subjects in image data included in the image content obtained by the obtaining circuit, to return the response, the control circuit modifies the image content so that persons other than a user who made an access request cannot be identified from other image data in which the persons are subjects, and presents a modified image content to the user who made the access request.

10. The access control device of claim 1 , wherein the persons are users of the access control device, the control circuit further manages permitted user information for each image content obtained by the obtaining circuit, each piece of the permitted user information indicating users who are permitted to access an image content obtained by the obtaining circuit, and if an image content obtained by the obtaining circuit includes image data including, as a subject, a user who is other than users indicated by a piece of the permitted user information associated with the image content, the control circuit modifies the image content so that persons other than the user cannot be identified from other image data in which the persons are subjects, and permits the user to access a modified image content.

11. An access control method for use in an access control device for controlling accesses by users to image contents each including still image data or video image data, the access control device including a storage circuit, an obtaining circuit and a control circuit, the access control method comprising the steps of: storing, by the storage circuit, first user information in association with each of one or more persons, each piece of the first user information being a set of identification information of one or more users who are permitted by a person to access image contents including image data in which the person is a subject; obtaining, by the obtaining circuit, an image content together with a piece of second user information, both having been transmitted from an external transmitter, the image content including image data in which one or more persons are subjects, and the piece of the second user information being a set of identification information of one or more users who are desired by the transmitter to be permitted to access the image content; extracting, from the first user information, one or more pieces of identification information of one or more users who are permitted by all of the one or more persons, who are the subjects of the image data included in the image content obtained by said obtaining of the image content, to access the image content, said extracting being performed by the control circuit; and permitting, by the control circuit, a user to access the image content when the user is included among the one or more users indicated by the piece of the second user information and is included among the one or more users indicated by the one or more pieces of identification information extracted by said extracting of the one or more pieces of identification information.

12. A non-transitory computer-readable recording medium having a program recorded thereon, the program for causing a computer to perform an access control method, the computer being provided in an access control device for controlling accesses by users to image contents each including still image data or video image data, the access control method comprising the steps of: storing first user information in association with each of one or more persons, each piece of the first user information being a set of identification information of one or more users who are permitted by a person to access image contents including image data in which the person is a subject; obtaining an image content together with a piece of second user information, both having been transmitted from an external transmitter, the image content including image data in which one or more persons are subjects, and the piece of the second user information being a set of identification information of one or more users who are desired by the transmitter to be permitted to access the image content; extracting, from the first user information, one or more pieces of identification information of one or more users who are permitted by all of the one or more persons, who are the subjects of the image data included in the image content obtained by said obtaining of the image content, to access the image content; and permitting a user to access the image content when the user is included among the one or more users indicated by the piece of the second user information and is included among the one or more users indicated by the one or more pieces of identification information extracted by said extracting of the one or more pieces of identification information.

13. An integrated circuit for use in an access control device for controlling accesses by users to image contents each including still image data or video image data, the integrated circuit comprising: a storage circuit storing first user information in association with each of one or more persons, each piece of the first user information being a set of identification information of one or more users who are permitted by a person to access image contents including image data in which the person is a subject; an obtaining circuit obtaining an image content together with a piece of second user information, both having been transmitted from an external transmitter, the image content including image data in which one or more persons are subjects, and the piece of the second user information being a set of identification information of one or more users who are desired by the transmitter to be permitted to access the image content; and a control circuit (i) extracting, from the first user information, one or more pieces of identification information of one or more users who are permitted by all of the one or more persons, who are the subjects of the image data included in the image content obtained by the obtaining circuit, to access the image content and (ii) permitting a user to access the image content when the user is included among the one or more users indicated by the piece of the second user information and is included among the one or more users indicated by the one or more pieces of identification information extracted by the control circuit.